Weird discharge!

Mariah
Okay so I'm not on birth control and my fiancé and I have unprotected sex often. I was supposed to start my period yesterday but I didn't and today I noticed when I wiped after I peed that I had a small amount of brown discharge. I'm aware of "old blood" after a period but never before....maybe old blood from implantation bleeding? Haven't taken a test yet...anyone else have this before?